This invention relates to a protective cap for an infrared radiation thermometer.
Infrared radiation thermometers are used for measuring body temperature. Typically, such a radiation thermometer includes a housing with a window admitting radiation, an internal optic system and an infrared sensor that is associated with an evaluation unit. The window admitting radiation serves to close off the interior of the housing of the radiation thermometer, thereby protecting the optic system and the sensor from contamination and destruction.
As an additional protection, protective caps of the type initially referred to are seated onto the end of the thermometer; such protective caps are described, for example, in EP-B1-0 201 790, U.S. Pat. No. 5,179,936 or U.S. Pat. No. 5,293,862. These protective caps not only serve the function of protecting the infrared transmitting window, but also are intended to prevent the transmission of diseases to the user, which is accomplished in that a new protective cap is installed prior to each temperature being taken or prior to each measurementxe2x80x94and this also in cases where different persons are involved. The disposable speculum as referred to in EP-B1-0 201 790, U.S. Pat. No. 5,179,936 or U.S. Pat. No. 5,293,862 is fitted over the ear canal probe of a tympanic thermometer that is sensitive to infrared radiation, this disposable speculum having an infrared transmitting membrane made of polypropylene or polyethylene. The portion carrying the membrane is an injection-molded part.
To determine a person""s body temperature, the forward end of the temperature measurement probe is inserted into the ear. The infrared radiation emitted by the tympanic membrane and by the ear canal enters the thermometer through the window and is incident, via the optic system or an optical waveguide and an interference filter, on the infrared sensor. The increase in temperature produced in the sensor results in an electrical output voltage from which the radiation temperature can be determined by means of an evaluation unit.
In such devices it has however shown that during measurement a temperature gradient occurs within the thermometer""s optic system due to contact of the ear with the thermometer""s generally cooler optic system, from which gradient a measurement error results usually. Moreover, the ear canal is subject to cooling by the thermometer. Because the thermometer detects also the infrared radiation of the ear canal or some other body cavity receiving the radiation thermometer, a further source of error results.
Proceeding from the state of the art referred to in the foregoing and the attendant problems of potential measurement errors, it is an object of the present invention to provide a protective cap protecting the user of such an infrared thermometer against the transmission of diseases, in addition to preventing the thermometer""s optic system from contamination. It is a still further object to avoid or at least substantially reduce the measurement errors of the type described in the foregoing that occur with conventional clinical thermometers equipped with protective cap.
In a protective cap of the type initially described, the foregoing object is attained according to a first invention in the form of a disposable probe cover for a tympanic thermometer of the type having a radiant energy sensing structure for sensing at least one wavelength of radiant energy emitted by the eardrum. The probe cover has an insertion end for insertion into an ear canal so as to communicate with the eardrum, and another end which remains outside of the ear canal so as to seal the ear canal. The probe cover insertion end includes a deformable foam body defining a passage that terminates in an opening. The passage accepts at least a part of the radiant energy sensing structure and communicates the radiant energy sensing structure with the opening. The probe cover further includes a barrier that substantially occludes the passage. This barrier prevents ear canal contaminants from entering the opening while, at the same time, substantially allowing radiant energy to pass therethrough and impinge upon the radiant energy sensing structure. Additional structures provide for insulation of precisely that portion of the base body that is in the immediate vicinity of the window and hence in intimate contact with the wall of the body cavity as, for example, the ear canal, in such fashion that in this particular portion the transfer of heat to the infrared optic system is reduced or maintained at such a low level as to be negligible as regards its effect on the temperature measurement. Because the thermal insulation of the protective cap reduces the passage of heat outside the window, the cooling of, for instance, the ear canal is also diminished at the same time. This has the further effect that by reason of the diminished cooling effect on the ear the user has the impression that the thermometer with this protective cap is warmer and hence substantially less discomforting.
Further, this thermally insulative means may be of a soft configuration, being more pleasant in the ear than a firm, non-pliant material or a protective cap sheathed with such a material. A further particular advantage of such a protective cap is to use it in conjunction with a clinical thermometer having a small probe tip. A clinical thermometer with a small probe tip is suitable for taking both an adult""s and a child""s temperature if the protective cap of thermally insulating material is made available in at least two sizes. However, such a protective cap may also be fabricated from a particularly soft, thermally insulating and hence elastic material which conforms itself to both an adult""s and a child""s ear canal, in spite of the size difference. According to the present invention, protective caps of this type are typically utilized as disposable protective caps.
To enable ease and nevertheless accuracy of positioning of the protective cap in the ear canal, but also to avoid different thermal effects due to different positions, at least the base body""s outer surface that comes into contact with the ear canal or also the base body""s entire outer surface outside the window area should be provided with the thermally insulative means. Such a configuration of the surface of the protective cap ensures at all times an adequate thermal insulation against the temperature measurement probe in the different positions of the clinical thermometer.
A further possibility for increasing the thermal insulation of the temperature measurement probe of the radiation thermometer includes providing the entire base body outside the window with thermally insulative means, that is, not only its outside but also its inside. With such an approach it is possible to prevent the thickness of the outer layer on the base body of thermally insulative means from becoming excessively thick, in addition to enabling the thermally insulative means on the inside to be dimensioned and set to an elasticity in such fashion as to achieve at the same time a clamping and yet detachable mounting of the protective cap on the end of the radiation thermometer.
The base body may at the same time serve as a stable support for the thermally insulating material which is affixed at least on the outside. A soft, porous foamed plastic material is preferably used as the thermally insulative means of the additional structure.
Another preferred possibility resides in that the additional structure is a body that is formed of one or several air chambers.
Pursuant to a further embodiment of the invention, the thermal insulative effects are enhanced still further. Preferably, in the protective cap structure comprising one or several air chambers, a flexible outer film is applied to the outside. Such an outer film forms at the same time a smooth outer surface offering little possibility for contaminants to collect and deposit during storage and stockkeeping of the protective caps.
As flexible outer film materials bounding, for instance, the air chamber or the air chambers of a thermally insulative means, polypropylene (PP), polyvinyl or polyethylene (PE) are proposed. For one thing, these are low-cost materials, for another thing, they are easy to process in order to manufacture the thermally insulating bodies, and moreover they are kind to the skin which is an essential aspect for the range of applications of clinical thermometers.
Where the additional structures of the thermally insulative means comprise air chambers, it may be convenient to provide several air chambers that are subdivided by fin members extending radially to the axis of the base body. While on the one hand this provides for sufficient flexibility of the thermally insulative means conveying a pleasurable feeling to the user, sufficient stability is imparted to the thermally insulative means in any direction on the other hand in order to make sure that the air chambers maintain dimensions sufficient for thermal insulation also in compressed condition. Moreover, the fin members may be formed of foamed plastic material in order to maintain the thermally insulating properties and prevent the formation of heat transfer bridges. Where applicable, the fin members may have apertures to connect adjacent air chambers in a fluid relationship to each other and hence increase the flexibility using a certain damping effect.
Preferably, the window of the radiation thermometer is formed by a window film transparent to infrared radiation or the actual window of the radiation thermometer is covered with such a film; in one embodiment, this window film may blend smoothly with a flexible outer film of the thermally insulative means covering the base body. To stabilize the protective cap, a holding device may be utilized, for example, in the form of an annular body which is attachable, for example, to the rim of the base body and keeps the film smooth.
According to the features of a further embodiment of the invention ease of manufacture of the protective cap results because it is not necessary to cover the window area during application of the additional structures, but rather, it is equally equipped with thermally insulating material. It is only subsequently that the window is formed by hot pressing, hot stamping or cold stamping. In this process, the air chambers and the foamed plastic material are pressed in such fashion that nearly clear transparent windows are produced.
As preferred material for the base body and the window, polyethylene (PE) or polypropylene (PP) is utilized. As preferred material for the additional structures serving as thermally insulative means in the form a thermally insulating foamed plastic, polyethylene (PE), polyvinyl or polyurethane (PU) is utilized, for example.
According to a second invention, the object of the present invention is attained than the protective cap, rather than having a base body, is fabricated only from a thermally insulating material such as foamed plastic or from a plastic material having air chambers. The window""s requisite thickness and transparency to infrared radiation are then obtained by hot stamping or cold stamping (claim 18).